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Working insulators begin failing as airborne contaminants and moisture from natural wetting combine on insulator surfaces to cause a drop in surface resistivity. This enables current to conduct across the insulators, thereby changing the electrical activity exhibited by the insulators when clean. If the drop in surface resistivity is severe enough, then the leakage current may escalate into a service interrupting flashover that degrades power quality. To help improve power quality, Texas A&M University developed an experimental methodology to investigate the electrical activity of contaminated insulators exposed to natural wetting. Leakage current and weather data obtained during experimentation showed that humidity and rain cause a deviation in the electrical activity of contaminated insulators from that of clean insulators. Analysis of leakage current data showed that this electrical activity was characterized by transient arcing behavior. Further, this nonsteady state activity is small, intermittent, and broad band in nature.
Date of Publication: April 2003